The objectives of this study are to: Define the mechanical characteristics of gastrointestinal and genitourinary sphincters, by determining their pressure-diameter, length force and stress-strain relationships; Determine the mechanism by which surgical corrective measures, such as fundoplication, modify the length-tension characteristics of the lower esophageal sphincter; Study the effect of pharmacologic, hormonal and electrical stimulation, and age related changes, on mechanical characteristics of gastrointestinal and genitourinary tract. BIBLIOGRAPHIC REFERENCES: Effect of oral metoclopramide on gastroesophageal reflux in the post-cibal state. J. Behar and P. Biancani. Gastroenterology 70: 331-335, 1976. Comparative pressure-length-diameter relationships of neonatal and adult rabbit ureters. M. Akamoto, P. Biancani, and R.M. Weiss. Invest. Urology 14: 297-300, 1977.